Exposure to the sun over time can induce many biochemical reactions in the skin. For example, exposure can lead to sunburn and tanning, which are immediate and well recognized. Other consequences of exposure to the sun are more subtle and accumulate over time. Often melanocytes can accumulate and the action of the enzyme tyrosinase is increased. These changes can result in the development of age spots and create an uneven, mottled skin tone. Unfortunately, many of the commercially available products in today's market are either only marginally effective, or contain active agents that are unstable and lose their potency when incorporated into a final formula.
The ability to modify the expression of pigment content in the skin, to promote an even-looking skin tone and a more youthful appearance, is highly desired in today's society. Many people desire to modify their skin tone, to reduce aging spots, melasma, etc., or for purely cosmetic reasons. In fact, in the Far East, a lighter skin tone is desirable and is associated with higher socioeconomic status.
Hyper-pigmentation in the skin is caused by the over expression or accumulation of melanin in the skin. As a result, the pathway involved in melanin production has been the target for many inhibitors so as to reduce the levels produced. One of the principal enzymes involved in the melanin pathway is tyrosinase.
Skin functions include, inter alia, protection, heat regulation, immune response, and sensory detection. With age, the skin's natural rejuvenation process slows. In addition, skin aging many times results in development of not only hyperpigmentation, but also hyperkeratinization wherein corneocytes adhere in excess causing a thickening of the stratum corneum. The stratum corneum comprises a portion of the epidermis, and includes nonviable corneocytes which are cells that have lost the nucleus and cytoplasm organelles.
What is needed is a composition which can be effectively used as a topically applied skin whitening agent. In addition, it is desirable to have a topical composition which can whiten skin as well as induce shedding of dry scales from the skin's surface thereby promoting a rejuvenated, fresher complexion. Applicant has now discovered a composition comprising tyrosinase inhibitors, and/or melanin cell synthesis inhibitors, in optional combination with skin exfoliating agents, which is useful in topically applied cosmetic and pharmaceutical formulations.